CN1816990A - Self-adaptive frame synchronization in general mobile telephone system receiver - Google Patents

Abstract

A Universal Mobile Telephone System (UMTS) receiver (115) performs slot synchronization using a received primary synchronization channel (PSCH) (205). Subsequent to completion of slot synchronization, the UMTS receiver (115) adaptively controls the duration of processing of the secondary synchronization channel (SSCH) (210) for determining frame synchronization.

Description

Adaptive Frame Synchronization in Universal Mobile Telephone System Receivers

technical field

The present invention relates generally to wireless receiving devices, and more particularly to user equipment (UE) in a spread spectrum based wireless system such as the Universal Mobile Telephone System (UMTS).

Background technique

The basic unit of time in a UMTS radio signal is the 10 millisecond (ms) radio frame, which is divided into 15 time slots of 2560 chips each. The UMTS radio signal from the cell (or base station) to the UMTS receiver is the "downlink signal", while the reverse radio signal is called the "uplink signal". When a UMTS receiver is first turned on, the UMTS receiver performs a "cell search" to search for a cell with which to communicate. Specifically, and explained below, initially the UMTS receiver looks for the downlink synchronization channel (SCH) sent from the cell to synchronize with at the slot and frame level and determines the cell specific scrambling code set. Voice/data communication can only be started after a successful cell search.

For cell search, SCH is a sparse downlink channel that is only valid during the first 256 chips of each time slot. The SCH consists of two sub-channels, the primary SCH (PSCH) and the secondary SCH (SSCH). The PSCH 256-chip sequence or PSCH code is the same in all slots of the SCH for all cells. Conversely, the SSCH 256 chip sequence, or SSCH code, can be different in each of the 15 slots of a radio frame and is used to identify one of 64 possible scrambling code groups. In other words, every radio frame of the SCH repeats the scrambling code group sequence associated with the respective transport cell. Each SSCH code is taken from the alphabet of 16 possible SSCH codes.

As part of the cell search, the UMTS receiver first uses the PSCH to achieve slot synchronization. In this regard, the UMTS receiver correlates the received samples of the received PSCH with the known PSCH 256-chip sequence (same for all slots), and from the position of the correlation peak, determines the slot reference time. When determining the slot reference time, the UMTS receiver is slot-synchronized and can determine the start time of each slot in a received radio frame.

After slot synchronization, the UMTS receiver stops processing PSCH and starts processing SSCH. Specifically, the UMTS receiver correlates a specific sequence of 15 SSCH codes in a received radio frame with a known sequence to achieve frame synchronization and determine the scrambling code group for the cell. Likewise, the identification of the scrambling code group enables the UMTS receiver to descramble all other downlink channels of the cell (eg Common Pilot Channel (CPICH)) in order to start voice/data communication.

Unfortunately, the SSCH portion of the cell search process described above is the most time-consuming portion. In particular, since a UMTS system may operate in a low signal-to-noise ratio, a UMTS receiver processes a predetermined number of received radio frames, eg 10 to 20, in order to obtain a good estimate of the sequence of 15 SSCH codes transmitted from the cell. Likewise, because each radio frame is 10 ms long, a user may experience a delay on the order of at least 100 to 200 ms before commencing voice/data communication.

Contents of the invention

As mentioned above, the UMTS receiver performs the SSCH part of the cell search by processing a predetermined number of received radio frames. However, it can be observed that the channel conditions allow that the UMTS receiver is able to acquire frame synchronization and successfully determine the scrambling code group after processing even one received radio frame. In other words, under some channel conditions, the UMTS receiver wastes time by processing unnecessary received radio frames. Thus, according to the principles of the present invention, a UMTS receiver receives an SCH channel comprising SSCH sub-channels, and adaptively controls the duration of SSCH-related processing for determining frame synchronization.

In an embodiment of the invention, the UMTS receiver is part of the UMTS User Equipment (UE). The UMTS receiver first performs slot synchronization using the PSCH and determines the peak correlation value associated with the received PSCH code. After achieving slot synchronization, the UMTS receiver then determines the number of received radio frames needed to determine frame synchronization as a function of determining the peak correlation value and possibly other correlation values. The UMTS receiver performs frame synchronization based on a predetermined number of received radio frames.

According to another embodiment of the invention, the UMTS receiver is part of a UMTS User Equipment (UE). UMTS receivers first use the PSCH to perform slot synchronization. After achieving slot synchronization, the UMTS receiver starts the frame synchronization process using the SSCH. During the frame synchronization process, the UMTS receiver checks after every received radio frame whether a scrambling code group can be determined. If the scrambling code group can be determined, the UMTS receiver stops SSCH processing of other received radio frames and completes frame synchronization and determination of scrambling codes.

Description of drawings

Figure 1 shows a portion of a demonstration wireless communication system in accordance with the principles of the present invention;

Figures 2 and 3 show an illustrative embodiment of a wireless receiver in accordance with the principles of the present invention;

Figure 4 shows a demonstration flow diagram according to the principles of the present invention;

Figure 5 shows a presentation frame table according to the principles of the present invention;

Figure 6 shows a demonstration pseudo-code implementation according to the principles of the present invention;

Figures 7 and 8 illustrate alternative implementations in accordance with the principles of the invention; and

9 and 10 show other demonstration flow diagrams in accordance with the principles of the invention.

Detailed ways

Apart from the inventive concept, the units shown in the figures are well known and will not be described in detail. Furthermore, it is assumed that UMTS-based wireless communication systems are well known and will not be described in detail here. For example, spread spectrum transmission and reception, cells (base stations), user equipments (UEs), downlink channels, uplink channels, and RAKE receivers are well known and will not be described here, except for the concept of the present invention. Furthermore, conventional programming techniques may be used to implement the concepts of the present invention, again not illustrated here. Finally, like numbers in the drawings indicate like elements.

An illustrative portion of a UMTS wireless communication system 10 in accordance with the principles of the present invention is shown in FIG. A cell (or base station) 15 broadcasts a downlink synchronization channel (SCH) signal 16 including the aforementioned PSCH and SSCH sub-channels. As mentioned above, the SCH signal 16 is synchronized by the UMTS user equipment (UE) as a prerequisite for voice/data communication. For example, a UE processes SCH signals during a "cell search" operation. In this example, a UE 20, such as a cellular phone, initiates a cell search when, for example, the UE 20 is turned on or powered on. The purposes of the cell search operation include (a) synchronizing cell transmissions at the slot and frame level of UMTS radio frames, and (b) determining the scrambling code group for a cell (eg, cell 15). As described below, and in accordance with the principles of the present invention, the UE 20 adaptively controls the duration of processing the SSCH portion of the SCH for determining frame synchronization. It should be noted that although the examples below show the inventive concepts in the context of an initial cell search (i.e. when the UE 20 is switched on), the inventive concepts are not limited thereto but are applicable to other examples of cell searches, For example when the UE is in "idle mode".

Turning now to FIG. 2, there is shown an illustrative block diagram of a portion of UE 20 in accordance with the principles of the present invention. The UE 20 includes a front end 105, an analog-to-digital (A/D) converter 110, a cell search unit 115, a searcher unit 120, a rake receiver 125, a host interface block 130, and a processor 135. It should also be noted that in addition to the concepts of the present invention, other elements known in the art may also be included in the blocks shown in FIG. 2 , however not illustrated for simplicity. For example, A/D converter 110 may include digital filters, buffers, and the like.

Front end 105 receives radio frequency (RF) signals 101 transmitted from cell 15 (FIG. 1) via an antenna (not shown) and provides baseband analog signals 106 representative of the PSCH and SSCH subchannels. The baseband analog signal 106 is sampled by an A/D converter 110 to provide a stream 111 of received samples. The received samples 111 are available for three components: a cell search unit 115 , a searcher unit 120 and a rake receiver 125 . The cell search unit 115 processes the PSCH and SSCH sub-channels according to the principles of the invention as will be described below. After a successful cell search, the searcher unit 120 estimates received samples for the multipath assignment to each finger of the rake receiver 125, which can be used, for example, for subsequent use by a decoder (not shown). OUT) decoded symbols are provided to combine data from multiple paths for voice/data communication. Because only the cell search unit 115 is relevant to the concepts of the present invention, the search component 120 and the rake receiver 125 are not further described here. The host interface block 130 connects data between the above three components and the processor 135 which receives the results from the cell search component 115 via signaling 134 in this context. Illustratively, processor 135 is a stored-program controller processor, such as a microprocessor, and includes memory 140 for storing programs and data.

Turning now to FIG. 3, an illustrative block diagram of the cell search unit 115 is shown. The cell search unit 115 includes a PSCH unit 205 and an SSCH unit 210 . Reference should now also be made to FIG. 4 , which shows a demonstration flow diagram for processing downlink PSCH and SSCH subchannels using the cell search unit 115 of FIG. 3 in accordance with the principles of the present invention. In step 305, the processor 135 of UE 20 starts cell search, and in step 305, attempts to realize time slot synchronization by processing the downlink PSCH sub-channel. Specifically, the processor 135 activates the PSCH unit 205 via the signaling 206 to process the received samples 111 as known in the art. For example, because the downlink PSCH sub-channel is a known PSCH 256 chip sequence or PSCH code that occurs periodically (i.e. repeats in each time slot of the downlink SCH signal), the PSCH unit 205 performs a process on the received sample 111 and the PSCH code Correlation, and provides the peak correlation value of the correlation. In this regard, PSCH unit 205 includes a matched filter and a buffer (neither of which is shown) that stores the output signal of the matched filter. PSCH unit 205 provides the peak correlation value to processor 135 via signaling 206 . The probability of "false lock" can be reduced by averaging this peak correlation value over a number of time slots (eg, four to twenty time slots) of received radio frames. (Because PSCH synchronization uses multiple time slots rather than frames, it is much faster than the prior art SSCH frame synchronization described above.) If the peak correlation value is not greater than a predetermined threshold, processor 135 controls PSCH unit 305 to continue processing any received signals , and continue to search for the cell. However, if the peak correlation value is greater than a predetermined threshold, UE 20 completes slot synchronization. An alternative approach is to consider slot synchronization complete when the peak correlation value exceeds the next highest correlation value by a predetermined additive or multiplicative factor.

In step 310, the processor 135 then adaptively determines the duration of the following SSCH processing as a function of the peak correlation value obtained from the time slot acquisition in accordance with the principles of the present invention. Specifically, the processor 135 determines the number of received frames to process frame synch as a function of the peak correlation determined in step 305 . In other words, the number of frame iterations of SSCH processing is based on, for example, the strength of PSCH correlation peaks indicative of the conditions of the communication channel. Although any function can be used, demonstratively, the number of frame iterations required for SSCH processing can be considered to be inversely proportional to the amount of primary SCH correlation peaks. For example, if the value of the PSCH correlation peak is very strong, above a predetermined level, only one frame of data is used for SSCH processing; whereas if the value of the PSCH correlation peak is very weak, perhaps two frames are processed, etc. In this regard, the processor 135 pre-correlates the PSCH correlation peak with the number of frames N required for SSCH processing, using the demonstrated frame number table or equivalent. Figure 5 shows a table 41 of such a demonstration. Illustratively, table 41 is stored in memory 140 of UE 20 . Each row of Table 41 correlates the PSCH correlation peak k _i with the number of frames N required for SSCH processing, where K _i >k _i+1 . For example, in step 310, if the correlation peak is greater than or equal to _ki , processor 135 controls SSCH processing to use only one received frame (N=1). It should be noted that the actual correlation peak and the number N of correlated frames are determined empirically, and will not be described here. Likewise, Table 41 may include arbitrary rows, depending on the empirically observed efficiency in SSCH processing. It is to be noted that other variants are also possible, eg the number N of frames may be determined as a function of a number of correlation values including or excluding the peak correlation value.

Turning to FIG. 4 , when the number of received frames to process has been determined, in step 315 processor 135 enables SSCH unit 210 to process received samples 111 for the determined number N of frames. The SSCH unit 210 is connected to the processor 135 via a signaling 211, and correlates the specific sequence of 15 SSCH codes in the received radio frame with a known sequence for achieving frame synchronization and for determining the scrambling code group of the cell (here is the scrambling code group related to cell 15). According to the principles of the invention, for the above-mentioned determined number N of received radio frames, SSCH processing is performed in order to average the correlation of successive frames of data to obtain a robust estimate of the received 15 SSCH code sequences. Obviously, if N=1, there are no consecutive frames. Note also that for simplicity, error conditions are not shown in the flowcharts described herein. For example, if the UE 20 loses slot synchronization while attempting frame synchronization, unfortunately, the above-mentioned cell search is restarted.

Apart from the concepts of the present invention, step 315 corresponds to SSCH processing as known in the art and is exemplarily performed by SSCH unit 210 and process 135 of FIGS. 2 and 3, respectively. As background, the UE 20 must determine one of the 64 scrambling code groups used by the cell 15, each scrambling code group being identified by a specific sequence of 15 SSCH codes. As used herein, 64 scrambling code groups form a scrambling code group set. In forming a scrambling code group, each SSCH code or symbol is derived from an alphabet of 16 symbols, eg 1 to 16. Likewise, a demonstrated scrambling code group, such as group 1, may include the following 15 SSCH symbols:

[1 1 2 8 9 10 15 8 10 16 2 7 15 7 16]

And another scrambling code group, such as group 2, may include the following 15 SSCH symbols:

[1 1 5 16 7 3 14 16 3 10 5 12 14 12 10]

However, because frame synchronization has not been achieved, the received sequence of a particular 15 SSCH codes may be shifted in position from each scrambling code group. In this regard, groups of scrambling codes are predefined in UMTS such that their cyclic shifts are unique, ie, the cyclic shift of any group of scrambling codes is different from any other group of scrambling codes. Therefore, since frame synchronization has not been achieved, the received sequence of the 15 received SSCH codes is compared with all 15 possible cyclic shifts of all 64 possible scrambling code groups to identify the received scrambling code groups and determine the Offset to get frame sync based on cyclic shift. (It should be noted that the cyclic shift includes a zero shift, i.e. there is actually no shift in the sequence of scrambling code groups.) This results in a comparison of (64)(15)=960 possible sequences, and typically, for 64 possible scrambling codes The 15 possible shifts in the code group and each scrambling code group are done in software in nested rings. Figure 6 shows a demonstrated pseudo-code implementation for comparing the received 15 SSCH code sequences with all 15 possible cyclic shifts of all 64 possible scrambling code groups to identify the received scrambling code group, And determine the frame offset. In Figure 6, it is noted that the comparison between the parameters peak_idx_buff (received samples) and the parameter code_groups (stored lookup table of 15 values for all 64 possible code groups) is performed (64)(15)(15) = 14400 Second-rate.

When the SSCH processing is successfully completed in step 315, the scrambling code group of the cell 15 is identified, enabling the UE 20 to descramble all other downlink channels of the cell (including, for example, the Common Pilot Channel (CPICH), for frequency synchronization, and also for The actual scrambling code group for the cell is determined based on the identified scrambling code group), and voice/data communication can begin.

It can be seen from the above that the processing load of comparing the received 15 SSCH code sequences with all 15 possible cyclic shifts of all 64 possible scrambling code groups is very large. However, according to the scheme of the present invention, the throughput can be reduced by exiting nested loops when a predetermined number of matches or mismatches are encountered for a given scrambling code group and shift. Fig. 7 shows a demonstration flow chart of an optional implementation among them. For this implementation, the following data is tracked by processor 135:

target_sequence - e.g. a specific cyclic shift for a specific scrambling code group of one of 960 possible group sequences

tentative_best_match - as the current best matching scrambling code group sequence of the received sequence, the initial setting is empty;

best_mismatches - tests the number of mismatches between the best match and the received sequence, initially set to the value 15;

mismatches - tests the number of matches between the best match and the received sequence, initially set to the value 0;

matches - the current number of matches between the received sequence and target_sequence; initially set to the value 0 at the beginning of each comparison. In step 605, a sequence of 15 SSCH codes is received for processing. Step 610 represents a comparison loop (hereinafter referred to as loop 610 ) comprising steps 611 and 612 . In step 611, the symbols of the received sequence are compared with the corresponding symbols of target_sequence (one of the 960 possible sequences mentioned above). As each symbol position is advanced, the respective variables mismatches and matches are updated appropriately. For example, if there is a specific comparison mismatch between received symbols and the respective symbols of target_sequence, increase the value of mismatches. Similarly, if there is a match, increment the value of matches. In step 612, the current mismatches value is compared with the best_mismatches value after each symbol comparison. If the value of mismatches is greater than or equal to the value of best_mismatches, processor 135 exits loop 610 and starts a new comparison of the received sequence with the next possible sequence (ie, the new target_sequence). Because a new comparison is started, the variables matches and mismatches are reset to 0 values. In other words, when the number of mismatches is equal to the mismatch of the current best match, the current search or comparison is abandoned. This saves processing time. Specifically, if a given received sequence has the same number of mismatches as the previous best matching sequence, the current comparison will not yield a better match, ie additional comparisons will not provide any additional information.

On the other hand, when the loop 610 ends the comparison between the received sequence and target_sequence without exiting the loop, a new better match is found. In this case, the variable tentative_best_match is updated with the target_sequence information (both about scrambling code groups and cycle offsets), the variable best_mismatches is updated with the value of mismatches, and the best_matches value is updated with the matches value. In step 615, the value of best_matches is compared to a predetermined threshold. If the value of best_matches is less than the predetermined threshold, the comparison with possible sequences continues in loop 610 as described above. However, if the value of best_matches is greater than or equal to a predetermined threshold, tentative_best_match is considered to be a received scrambling code group, and the associated cyclic shift is used to determine the frame offset. The predetermined threshold may be set to a value representing an exact match, such as 15; or may be set to a lower value, such as 10 matches. The use of fewer than 15 matches may be preferable under poor signal-to-noise ratio conditions, since it may not be possible to obtain a perfect match. This user-defined threshold of less than 15 can be chosen to be high enough to guarantee, with some probability of success, that the wrong sequence will not be chosen by accident. FIG. 8 shows an exemplary pseudo-code implementation of the method of FIG. 7 .

As described above, the processor 135 adaptively determines the duration of the following SSCH processing as a function of the peak correlation value obtained according to the time slot. In the embodiments described above, the processor 135 determines the number N of frames to process. However, other selection methods are possible in accordance with the principles of the present invention. Turning now to FIG. 9, another illustrative embodiment is shown. In this demonstrative embodiment, after each frame iteration, accumulated data representing 15 SSCH codes is examined. If there are enough matches to identify a particular sequence of 15 SSCH codes, processor 135 suspends SSCH processing. Likewise, SSCH processing can be suspended even after one received radio frame has been processed. Specifically, the processor 135 enables SSCH processing after the aforementioned acquisition of slot synchronization (eg, represented by step 305 of FIG. 4 ). In step 405 of FIG. 9, the SSCH unit 210 processes received radio frames, one frame at a time, as described above. As a result of this processing, in step 410 the SSCH unit 210 accumulates over time correlation values for the sequence of 15 received SSCH codes as each successive frame is processed. In steps 405 and 410, SSCH unit 210 continues to process each received frame and accumulate data based on time until paused by processor 135 (described below). In step 415, processor 135 determines the number of matches between the SSCH code (possible scrambling code group) represented by the accumulated correlation value and each of the 64 scrambling code groups of the scrambling code group set. For example, if the accumulated correlation values from step 410 represent the following received SSCH sequences (sets of possible scrambling codes):

[1 1 2 8 9 5 5 5 5 5 5 5 5 5 5],

There may then be five matches associated with scrambling code group 1, and only two matches associated with scrambling code group 2 (group 1 and group 2 are defined demonstratively above).

Continuing with the flowchart of FIG. 9, in step 420, the processor 135 determines whether the number of matches exceeds a predetermined threshold, eg, a match of at least 13 SSCH codes of a scrambling code group of the scrambling code group set out of a maximum of 15 possible matches. If none of the scrambling code groups of the set of scrambling code groups have a match with an associated number exceeding the predetermined threshold, then in step 415 the processor 135 continues processing and after processing the next received frame by the SSCH unit 210, checks the updated accumulated related value. However, if the number of matches for one of the scrambling code groups of the scrambling code group set exceeds a predetermined threshold, SSCH processing is suspended in step 425 and the scrambling code group is selected as the scrambling code group in step 430 from the scrambling code group set. As mentioned above, when the SSCH processing is completed and the scrambling code group of the cell 15 is identified in step 430, the UE 20 can descramble all other downlink channels of the cell (including, for example, the Common Pilot Channel (CPICH) for frequency synchronization, It is also used to determine the actual scrambling code group of the cell from the identified scrambling code groups), and voice/data communication can be started.

It can be seen from FIG. 9 that there are cases where multiple scrambling code groups have correlated matching numbers. For example, assume that scrambling code group 5 is:

[1 2 3 4 5 6 7 8 9 10 11 12 13 14 15],

Scrambling code group 7 is:

[15 14 13 12 11 10 9 8 7 6 5 4 3 2 1], and the accumulated correlation values from step 410 represent the following received SSCH sequences (sets of possible scrambling codes):

[1 2 3 4 5 5 5 5 5 5 4 3 2 1].

If the threshold for the predetermined number of matches in step 420 is illustratively set to five, there are five matches for scrambling code group 5 and scrambling code group 7 of the scrambling code group set. In this case, the selection of a specific set of scrambling codes is unreliable. The flowchart shown in Figure 10 adds an additional step 435 of selecting the scrambling code group with the most matches from the set of scrambling code groups when a predetermined threshold is exceeded. If no scrambling code group has the most matches, processing continues at step 415 as described above. However, if one scrambling code group does have the most matches, SSCH processing is suspended in step 425 and that scrambling code group of the scrambling code group set is selected as the scrambling code group in step 430 .

As described above, in accordance with the principles of the present invention, a wireless receiver adaptively determines the duration of SSCH processing to reduce the number of received frames processed to the minimum number of received frames processed to achieve frame synchronization. Although described in the context of an initial cell search process, the concepts of the present invention are applicable to any part of radio operation that deals with downlink channels (eg, SSCH sub-channels) in the presence of changing channel conditions.

The foregoing merely illustrates the principles of the invention, and it will thus be appreciated that various alternative arrangements can be devised by those skilled in the art that, although not explicitly shown herein, embody the principles of the invention and remain within its spirit and scope. For example, although shown in the context of separate functional units, the integrated circuit (IC) may be implemented in one or more integrated circuits (ICs) and/or in one or more stored program control processors such as microprocessors or digital signal processors ( DSP)) realize these functional units. Similarly, although demonstrated in the context of a UMTS based system, the present invention is applicable to any communication system that processes signals in the presence of varying channel conditions. It is therefore to be understood that various modifications may be made to the illustrated embodiments, and that other arrangements may be devised, without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (20)

1. A method for use in a wireless receiver, comprising: processing the first synchronization channel (305) of the received wireless signal to obtain slot synchronization; and A duration of processing a second synchronization channel of the received wireless signal is adaptively controlled to obtain frame synchronization (310). 2. The method of claim 1, wherein the first synchronization channel is a primary synchronization sub-channel (PSCH) of Universal Mobile Telephone System (UMTS), and the second synchronization channel is a secondary synchronization sub-channel (SSCH). 3. The method of claim 1, wherein the step of processing the first synchronization channel comprises the step of providing a peak correlation value associated with the first synchronization channel. 4. The method of claim 3, wherein the step of adaptively controlling comprises the step of: determining the number of received frames of the received wireless signal as a function of the peak correlation value; and Based on the determined number of frames, the second synchronization channel is processed to obtain frame synchronization. 5. The method of claim 4, wherein processing the second synchronization channel comprises the steps of: comparing the estimated received sequence to each of a plurality of possible received sequences, each sequence comprising a plurality of symbols; and identifying one of the plurality of possible sequences as the best possible match after each comparison with one of the plurality of possible sequences; Wherein, in the comparing step, if the number of mismatches in the current comparison is greater than or equal to the number of mismatches associated with the best possible match, the current comparison is discarded and a new comparison is started. 6. The method of claim 1, wherein the step of processing the first synchronization channel comprises the step of providing a plurality of correlation values associated with the first synchronization channel, the plurality of correlation values including a peak correlation value. 7. The method of claim 6, wherein the step of adaptively controlling comprises the step of: determining a number of received frames of the received wireless signal as a function of the peak correlation value and at least one other value; and Based on the determined number of frames, the second synchronization channel is processed to obtain frame synchronization. 8. The method of claim 7, wherein the step of processing the second synchronization channel comprises the steps of: correlating the received wireless signals based on a predetermined number of frames to provide an estimate of the received sequence; and comparing the estimated received sequence to each of the plurality of expected received sequences to determine the number of matches thereto; and If the number of matches for at least one of the plurality of expected received sequences exceeds a predetermined threshold, the step of processing the second synchronization channel is exited. 9. The method of claim 1, wherein the step of adaptively controlling comprises the step of: processing the second synchronization channel to form accumulated data representing groups of possible scrambling codes comprising sequences of M symbols; determining the number of matches between the sequence of M symbols of the possible scrambling code groups and each of the scrambling code groups in the set of scrambling code groups; and If the determined matching number of at least one scrambling code group of the scrambling code group set exceeds a predetermined value, selecting the at least one scrambling code group as the scrambling code group used in acquiring frame synchronization. 10. A method according to claim 9, wherein the step of selecting comprises the step of suspending further processing of the received frame in the received radio signal. 11. The method of claim 9, wherein the selecting step comprises the step of: If more than one scrambling code group of the set of scrambling code groups exceeds the predetermined number of matches, the scrambling code group with the highest number of matches is selected. 12. A method for use in a wireless receiver, comprising: processing (305) a first synchronization channel of wireless signals received from the wireless communication channel to obtain time slot synchronization for providing a signal indicative of a condition of the wireless communication channel; using the value of the signal that is compiled into a table for determining the number of received frames; and A second synchronization channel of the wireless signal is processed to obtain frame synchronization based at least on the determined number of frames. 13. The method of claim 12, wherein processing the second synchronization channel comprises the steps of: comparing the estimated received sequence to each of a plurality of possible received sequences, each sequence comprising a plurality of symbols; and identifying one of the plurality of possible sequences as the best possible match after each comparison with one of the plurality of possible sequences; Wherein, in the comparing step, if the number of mismatches in the current comparison is greater than or equal to the number of mismatches associated with the best possible match, the current comparison is discarded and a new comparison is started. 14. A Universal Mobile Telephone System (UMTS) device comprising: a front end (105) for receiving a wireless signal representing a sequence of frames and for providing therefrom a stream of received samples; and A processor (135) for adaptively controlling a duration for performing frame synchronization on received samples. 15. The UMTS device of claim 14, further comprising: a master synchronization unit (205) operating on the received samples for acquiring time slot synchronization to the master synchronization signal of the received wireless signal and for providing a peak correlation value associated therewith; and a secondary synchronization unit (210), operable on the received samples, for acquiring frame synchronization of the secondary synchronization signal of the received wireless signal; Wherein, the processor determines the number of frames required by the sub-synchronization unit for obtaining frame synchronization processing according to the function of the peak correlation value. 16. The UMTS device of claim 15, wherein, as a function of the peak correlation value and the at least one other correlation value, the processor determines the number of frames required by the secondary synchronization unit to obtain frame synchronization processing. 17. The UMTS device of claim 14, further comprising: a master synchronization unit (205) operating on the received samples for acquiring time slot synchronization to the master synchronization signal of the received radio signal; and a secondary synchronization unit (210) operating on received samples after slot synchronization to provide a set of possible scrambling codes comprising a sequence of M symbols; Wherein, the processor (a) determines the number of matches between the M-symbol sequences of the possible scrambling code groups and each scrambling code group of the scrambling code group set; and (b) if the determination of at least one scrambling code group of the scrambling code group set The matching number exceeds a predetermined value, and the at least one scrambling code group is selected as a scrambling code group for obtaining frame synchronization. 18. The UMTS device of claim 17, wherein the processor suspends further processing of the received frame in the received radio signal if the determined number of matches of at least one scrambling code group exceeds a predetermined value. 19. The UMTS device of claim 17, wherein if more than one scrambling code group of the set of scrambling code groups exceeds the determined number of matches, the processor selects the scrambling code group with the highest number of matches. 20. A Universal Mobile Telephone System (UMTS) device comprising: A front end (105), configured to receive a wireless signal representing a sequence of frames, each frame including a primary synchronization signal and a secondary synchronization signal; a memory (140) for storing a table associating numbers of received frames with correlation values correlated with received primary synchronization signals; and A processor (135) that limits processing of the secondary synchronization signal to an associated number of received frames.

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